Effects of cabergoline on reproduction in three families of Australian marsupials

Abstract

The effects of the prolactin inhibiting drug, cabergoline, on pregnant and lactating marsupials were investigated in four species from three diverse families: the tammar wallaby, Macropus eugenii, the quokka, Setonix branchyurus, the brushtail possum, Trichosurus vulpecula, and the fat-tailed dunnart, Smithopsis crassicaudata. In tammar wallabies, 20 μg cabergoline kg-1 injected intramuscularly 1 day before expected birth did not alter the timing of parturition but neonates died within a day of birth, suggesting that the onset of lactation was compromised. During early lactation in tammars (56-69 days post partum), an intramuscular injection transiently retarded growth of the young, although they subsequently survived. This treatment induced reactivation of the quiescent corpus luteum and the blastocyst from diapause, so a new birth occurred 26-27 days later, despite the continued sucking of the young in the pouch. Intramuscular injection during late lactation (166 - 199 days post partum) apparently suppressed milk secretion since pouch young lost up to 20% of their bodyweight or died within 7 days of treatment. Oral administration of cabergoline had no effect on the growth of the young or on the quiescent corpus luteum and diapausing blastocyst. Quokkas showed similar responses to tammars after treatment in late lactation. Possums and dunnarts were less sensitive to injected cabergoline than the two macropodid species, and possums showed no response to oral administration. The lack of response of these marsupial species to oral cabergoline treatment suggests that accidental ingestion of baits, containing 20 μg cabergoline kg-1, used to control introduced eutherian pests such as the red fox, Vulpes vulpes, or the feral cat, Felis cattus, should not affect the reproduction of native marsupials.